UC-NRLF 


*B    313    Ebl 


LIBRARY 

OF  THE 

University  of  California. 

r^  GIFT    OF 
^A<J^..:,^^^^ 

Class 


lui  uauis  mu^^  Bi.i!*''- 


WAR  DEPARTMENT 
OFFICE  OF  THE  CHIEF  OF  STAFF  ::  WASHINGTON 


QUESTIONS  AND  ANSWERS 
FOR  USE  IN  THE  INSTRUC- 
TION OF  TORPEDO  COMPA- 
NIES AND  DETACHMENTS 

(NEW  SYSTEM) 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 

1908 


'  "^  rs 


WAR  DEPARTMENT. 

Document  No.  310. 
Office  of  the  Chief  of  Staff. 

(2) 


rC^ 


OFTHE  ^ 

UNfVERSITY    J 

or  / 

QUESTIONS   AND  ANSWERS 

§FOR  USE  IN  THE 
Instruction  of  Torpedo  Companies  and 
Detachments. 

(NEW  SYSTEM.) 


Upon  the  recommendation  of  the  Chief  of  Artillery, 
approved  by  the  Secretary  of  War,  the  following  is 
issued  as  a  guide  in  the  instruction  of  enlisted  men  in 
companies  and  detachments  assigned  to  mine  defense 
where  the  new  system  is  installed. 

MATERIAL  OF,  AND  DUTIES  IN,  THE  LOADING  ROOM. 

1.  What  apparatus  is  used  in  making  a  turk^s  head? 

A  navy  knife,  1  pair  cutting  pliers,  1  hammer,  1 
turk's  head  collar  (large  or  small),  14  feet  marline,  are 
required. 

2.  What  is  used  in  making  a  telegraph  joint? 

Cutting  pliers,  navy  knife,  and  a  small  file.  If  the 
joint  is  to  be  insulated  add  rubber  tape. 

3.  What  is  used  in  making  a  joint  to  be  put  under  water? 
A   navy   knife,   cutting   pliers,   file,   rubber   cement, 

rubber  tape,  tinfoil,  and  protective  tape.     A  torch,  or 

(3) 
±  VJ»  ^  tL/  o  v> 


waste  saturated  with  alcohol  or  oil,  is  needed  for  vul- 
canizing the  joint.  Brass  jointers  are  used  when 
authorized. 

Before  placing  the  joint  in  water,  the  turk's  heads 
must  be  clamped  in  a  distribution  box  or  junction  box. 

4.  Name  all  the  parts  of  an  assembled  m.iiie. 

Mine  case,  mine  cap,  compound  plug,  complete— in- 
cluding plug  proper,  lower  tube,  fuze  can  cap,  fuze  can, 
mine  transformer,  ball  seat,  circuit-closer  case,  distance 
ring,  springs,  steel  ball,  2  brass  washers,  2  rubber  pack- 
ings, 1  brass  follower,  1  steel  follower,  3  lead  washers, 
and  set  screws ;  loading  wire,  "  C "  wire,  priming 
charge,  2  fuzes,  100  pounds  of  explosive,  and  ruberine. 

5.  Explain  how  to  prepare  a  compound  plug. 

The  transformer  to  be  used  is  first  tested  for  a  good 
circuit  between  the  red  wires,  a  poor  circuit  between  the 
black  wires,  no  circuit  between  the  red  and  black  wires, 
and  no  circuit  between  either  wire  and  case.  The  upper 
black  resistance  terminal  is  cut  to  1^  inches  in  length, 
the  end  bared,  and  then  clamped  in  the  terminal  stud 
in  the  neck  of  the  transformer.  The  ball  seat  is  then 
screwed  home  and  the  ball  put  in  place.  The  circuit- 
closer  case  containing  springs,  distance  ring  and  steel 
ball  is  then  screwed  home.  (In  preparing  mines  for 
service,  before  screwing  up  the  threads  of  the  circuit 
closer,  transformer,  fuze  can,  and  plug  proper  are 
coated  with  ruberine  or  some  similar  waterproofing 
material.  This  is  omitted  when  compound  plugs  are 
prepared  for  drill  or  for  instruction  purposes.)    A  piece 


of  "A"  or  loading  wire,  20  feet  in  length,  is  fastened  by 
a  telegraph  joint  to  the  primary  terminal  and  the  joint 
is  taped.  This  length  is  for  convenience  in  testing  and 
is  cut  off  15  inches  from  the  compound  plug  when  the 
mine  is  assembled  for  planting.  This  wire  and  the  two 
secondary  wires  are  drawn  through  the  fuze  can,  which 
is  then  screwed  on  the  transformer. 

Two  fuzes  which  have  been  tested  for  continuity  of 
circuit  are  put  on  by  telegraph  or  jointers  joint  in  mul- 
tiple across  the  secondary  (red)  terminals  and  the 
joints  taped.  The  primer  charge,  about  1  pound  of 
dynamite,  is  put  in  a  cloth  bag  provided  for  the  pur- 
pose, the  fuzes  embedded  in  the  charge  and  the  bag 
tightly  tied  around  the  neck.  The  charge  is  then 
pushed  up  in  the  fuze  can.  The  loading  wire  is  drawn 
through  the  fuze-can  cap,  a  rubber  packing  pushed 
over  it  into  its  stuffing  box,  and  a  brass  washer  is 
threaded  down  so  that  it  is  close  against  the  rubber 
packing.  The  follower  is  then  screwed  home  with 
moderate  pressure,  and  the  lower  tube  is  screwed  into 
place,  compressing  a  lead  washer  between  it  and  the 
fuze-can  cap.  The  loading  wire  is  drawn  through  the 
hole  in  the  plug  proper  and  the  latter  screwed  hard 
against  the  lower  tube,  a  lead  washer  being  used  be- 
tween them. 

A  rubber  packing  and  brass  washer  are  now  placed 
upon  the  loading  wire  and  forced  into  their  seats  in 
the  plug  proper  by  means  of  the  follower,  as  in  the  case 
of  the  fuze-can  cap.  Special  care  must  be  exercised  in 
.forcing  the  followers  home,  as  the  insulation  of  the 
loading  wire  is  liable  to  be  pinched  if  the  rubber  pack- 


6 

ings  are  squeezed  down  too  much.  The  plug  is  then 
tested  with  a  circuit  detector  for  poor  circuit  when  in 
vertical  position  and  for  good  circuit  when  turned  be- 
yond 45°.  When  a  transformer  is  used,  as  in  this  sys- 
tem, this  test  may  be  made  without  any  danger. 

If  it  is  desired  to  record  the  actual  resistance  with 
the  plug  in  vertical  and  horizontal  positions,  this  may 
be  done  by  testing  with  a  voltmeter;  it  is  not  really 
necessary  and  would  be  omitted  if  there  were  not  an 
abundance  of  time. 

In  service  if  the  loaded  plug  tests  out  satisfactorily 
all  set  screws  are  then  set  up. 

•Continuity  of  circuit  of  fuzes  should  be  tested  only 
under  specific  instructions  of  a  commissioned  officer. 

6.  What  apparatus  is  used  in  preparing  a  compound  plug? 
Compound  plug  complete,  as  described  in  (4),  bench 

vise,  S-wrench,  large  monkey  wrench,  screw-driver, 
small  pliers,  navy  knife,  loading  wire,  cotton  braided 
wire,  priming  charge,  fuzes,  rubber  packings,  brass 
washers,  followers,  lead  washers,  set  screws,  red  lead 
or  ruberine,  circuit  detector,  brass  jointers,  rubber  tape. 

7.  How  are  mines  numbered? 

Facing  the  direction  from  which  the  enemy  is  ex- 
pected the  mines  in  each  group  are  numbered  from  left 
to  right — No.  1  on  the  left. 

Groups  are  numbered  in  a  similar  way;  the  outer 
left-hand  group  is  No.  1,  the' next  one  to  the  right  is  No. 
2,  and  so  on  through  outer  line ;  the  left-hand  group  of 
next  line  has  the  number  following  that  of  the  right; 
hand  group  of  first  line. 


8.   How  are  the  mooring  ropes  prepared,   and  what  are  the 
rules  for  length  of  mine  cables  and  of  mooring  ropes? 

The  mooring  cables  are  cut  off  with  square  ends  and 
the  ends  passed  through  the  holes  in  the  mooring  sock- 
ets. The  strands  and  wires  are  untwisted  and  spread 
out  for  a  length  equal  to  the  length  of  the  socket  hole. 
The  rope  is  then  pulled  back  until  the  loose  ends  are 
about  flush  with  the  top  edge  of  the  hole;  a  piece  of 
marline  is  tied  about  the  rope  below  the  socket.  If  nec- 
essary to  hold  the  socket  a  piece  of  burlap  may  be 
wrapped  around  below  the  socket  and  a  fold  allowed  to 
fall  over  the  hand.  Generally  means  can  be  found  to 
set  the  socket  upright  while  pouring  full  of  alloy. 
Great  care  must  be  taken  to  see  that  there  is  no  water 
or  surplus  oil  on  the  socket  or  mooring  rope  before 
pouring  the  alloy. 

Mines  are  planted  with  a  submergence  of  5  feet  be- 
low mean  low  water. 

Where  ordinary  anchors  are  used  the  mooring  ropes 
must  be  prepared  for  depths  obtained  by  sounding.  If 
sockets  are  used,  the  ropes  for  No.  32  cases  are  but  10 
feet  less  than  the  ascertained  depths  at  mean  low  water. 
This  allows  5  feet  for  submergence  and  5  feet  for  the 
mine,  mine  bail,  sockets,  shackles,  and  anchor.  For  the 
larger  mine  cases  an  additional  allowance  must  be  made 
for  the  length  of  the  cylindrical  part  of  the  case. 
Finally  each  mooring  rope  is  tagged  at  each  end  w^ith 
the  number  of  the  corresponding  mine. 

Mine  cables  are  cut  to  the  following  lengths  plus 
twice  the  approximate  depth  of  water; 


Feet. 

Feet. 

No.  1 

1,425 

No.  11 

425 

No.  2 

1,225 

No.  12 

475 

No.  3 

1,025 

No.  13 

525 

No.  4 

825 

No.  14 

625 

No.  5 

_      _            725 

No.  15 

725 

No.  6 

G25 

No.  16 

825 

No.  7      • 

525 

No.  17 

No.  18 

1,  025 

No.  8 

475 

1,225 

No.  9 

425 

No.  19 

1,425 

No.  10 

375 

Each  end  of  each  cable  is  tagged  with  the  number  of 
the  corresponding  mine. 

MATERIAL  FOR  AND  DUTIES  ON  THE  WATER. 

1.   What    apparatus    is   taken   out    on   the   distribution    box 
boat? 

One  distribution  box,  1  buo}^  for  same,  1  mooring 
rope  for  attaching  buoy  to  distribution  box,  1  anchor 
sufficiently  heavy  to  hold  distribution  box  boat,  1  an- 
chor buoy  (keg)  and  rope  for  same,  2  anchor  shackles 
(1  for  anchor  and  1  for  box),  1  pair  field  glasses,  alco- 
hol, 2  alcohol  lamps,  cable  tags,  turk's  head,  collars,  cot- 
ton waste,  2  files,  2  hammers,  2  heaving  lines,  knives, 
marline,  2  marline  spikes,  1  megaphone,  2  monkey 
wrenches,  2  pliers,  protective  tape,  rubber  cement,  rub- 
ber tape,.  2  scissors,  tinfoil,  telephone,  brass  connectors, 
lashings. 

The  planter  may  locate  the  distribution  box  boat  an- 
chor and  in  that  case  it,  together  with  its  buoy  and 
rope,  would  not  be  taken  out  in  the  distribution  box 
boat. 


2.  How  and  in  what  way  are  the  cores  of  cable  numbered? 
They  are  numbered  by  the  noncommissioned  officer 

in  charge  of  the  boat,  who  establishes  communication 
with  the  casemate,  using  the  bo^t  telephone,  and  work- 
ing under  the  instructions  of  the  casemate  electrician. 

Nos.  1,  13,  and  19  are  easily  selected  by  means  of 
their  special  marking ;  No.  19  is  the  center  core ;  No.  13 
is  the  marked  core  in  the  inner  row  of  six,  and  No.  1  is 
the  marked  core  in  the  outer  row  of  twelve. 

In  the  seven-cored  cable  there  are  no  marked  cores, 
the  cores  being  numbered  under  instructions  of  the 
casemate  electrician. 

3.  How  is  a  mine,  together  with  its  attachments,  arranged 

for  planting? 

A  reel  of  single  conductor  cable  is  placed  on  board 
the  planter  and  put  on  the  jacks.  A  piece  SO  feet  long 
is  cut  off  the  end  to  eliminate  the  part  which  was  above 
water  during  storage.  The  cables  for  the  mines  are 
now  unreeled,  cut  to  the  prescribed  lengths  and  tagged 
with  the  number  of  the  corresponding  mine. 

The  cable  for  No.  19  mine  is  carried  back  on  the  port 
side  and  coiled  in  a  figure  eight  on  the  after  deck,  the 
tagged  ends  being  brought  up  forward.  The  figure 
eight  is  lashed  with  pieces  of  small  rope  around  the 
center  and  at  the  turns.  A  mine  cap  is  slipped  over 
the  end  from  the  bottom  of  the  coil  and  turk's  heads 
are  made  on  each  end. 

The  cable  for  No.  1  mine  is  prepared  likewise,  being 
carried  back  on  the  starboard  side.  This  is  repeated 
until  all  nineteen  cables  are  ready ;  the  coils  are  piled  on 


10 

top  of  each  other.  The  cables  for  Nos.  1  to  9  are  on  the 
starboard  side,  those  for  Nos.  10  to  19  are  on  the  port 
side. 

While  the  cables  are  being  prepared  the  mine  buoys, 
anchors,  mooring  ropes,  raising  ropes,  shackles,  sister 
hooks,  etc.,  are  gotten  aboard  and  placed  forward,  the 
proper  supply  on  either  side.  The  anchors  are  placed 
as  convenient  to  the  forward  davits  as  possible. 
,  Finally  the  loaded  mines  are  put  aboard.  If  they 
contain  dynamite  they  should  be  protected  from  the 
direct  rays  of  the  sun  by  being  covered  with  paulin. 

The  detail  on  each  side  of  the  planter  prepares  a 
mine  on  its  own  side.  The  loading  wire  from  the  mine 
is  cut  to  the  proper  length,  a  taped  joint  is  made  with 
the  single  conductor  of  the  corresponding  cable,  and  the 
mine  cap  is  fastened  on.  The  cable  is  lashed  with  mar- 
line to  the  bales  just  above  the  ring. 

The  proper  mooring  rope  is  now  shackled  at  one  end 
to  an  anchor,  at  the  other  end  to  the  mine,  and  is  lashed 
to  the  mine  cable  with  marline  at  every  5  feet.  (If 
automatic  anchors  be  used,  this  lashing  is  omitted.) 

A  rope  for  raising  the  mine  is  cut  to  the  length  of  50 
feet  plus  the  depth  of  water.  One  end  is  attached  to 
the  anchor  by  an  anchor  knot,  the  other  to  the  mine 
cable  by  two  half  hitches  and  a  seizing  of  marline.  It 
should  not  be  secured  at  other  points.  The  use  of  this 
is  explained  later.    • 

The  mine  buoys  have  attached  to  them  60  feet  of 
small  rope,  w^hich  is  marked  at  every  5  feet.  The  free 
end  is  slipped  through  the  maneuvering  ring  of  the 
mine  and  tied  to  the  buoy. 


11 

The  anchor  is  now  slung  to  a  tripping  hook  below  a 
differential  block  on  the  forward  davit  and  is  hoisted 
and  swung  clear  of  the  rail.  The  mine  is  similarly 
slung  by  its  maneuvering  ring  from  the  after  davit  and 
a  heaving  Jine  is  bent  onto  the  free  end  of  the  mir^e 
cable.  Both  mine  and  anchor  are  lowered  as  close  to 
the  water  as  conditions  will  permit.  Before  slinging 
the  mine  and  anchor  the  release  of  the  tripping  hook 
must  be  lashed  well  with  marline,  which  is  cut  after 
they  have  been  lowered.  A  mousing  must  also  be  put 
around  the  upper  hook  of  the  differential  block.  The 
aft  detail  now  removes  or  cuts  the  rope  lashings  of  the 
coil  of  the  corresponding  mine  cable  and  sees  that  all 
cables,  ropes,  etc.,  are  cleared  ready  for  planting. 

The  planter  moves  out  toward  the  buoyed  line  and 
passes  as  close  as  possible  to  the  distribution  box  boat, 
with  the  latter  to  port.  As  it  passes  slowly  by,  the 
heaving  line  is  thrown  by  a  man  well  forward  to  the 
distribution  box  boat,  whose  party  immediately  haul  in 
the  mine  cable,  insert  the  turk's  head  in  the  correspond- 
ing slot.  No.  -10,  of  the  distribution  box,  and  lash  the 
cable  to  the  boat.  (If  the  water  be  rough,  the  cable 
end  is  passed  to  the  boat  by  a  launch.) 

The  planter  then  moves  out  to  the  central  buoy 
which  marks  the  position  of  mine  No.  10.  As  the  for- 
ward davit  comes  abreast  of  the  buoy,  the  officer  in 
charge  of  the  planting  commands  "  Let  go ;  "  the  trip- 
ping hook  of  the  anchor  is  released  first  and  that  of  the 
mine  immediately  thereafter. 


12 

(Caution. — The  men  operating  the  tripping  hooks 
must  he  very  careful  that  they  stand  hack  of  all  cahle. 
rope^  etc,^  so  that  they  may  not  he  caught.  All  others 
must  stand  clear.) 

.  The  planter  then  executes  a  sweeping  circle  to  star- 
board, passes  to  the  rear  and  comes  up  with  the  distri- 
bution box  boat  to  starboard.  As  it  moves  by,  the  free 
end  of  mine  cable  No.  9  is  passed  to  the  boat  and  secured 
as  before.  The  planter  moves  ahead  to  a  point  100  feet 
to  the  left  of  mine  No.  10,  and  as  it  crosses  the  line 
plants  mine  No.  9,  swings  otf  to  port,  circles  and  comes 
up  from  the  rear  with  the  distribution  box  boat  to  port, 
and  so  on  alternately  until  all  the  mines  are  planted. 

As  soon  as  a  mine  is  dropped,  the  detail  for  that  side 
of  the  planter  prepares  another  for  planting.    There  is 
ample  time  to  do  this  while  the  vessel  is  turning  and 
planting  the  other  mine. 
4.   Name  the  apparatus  on  the  boat  used  in  planting  mines. 

Derricks,  catheads,  snatch  blocks,  steam  winches, 
insulated  cable,  cable-drum  frames,  circuit  detector, 
boat  hooks,  sounding  lines  graduated  to  feet,  davits, 
differential  blocks,  mooring  ropes,  raising  ropes,  buoy- 
ant mines  and  anchors,  shackles  and  extra  split  pins  for 
same,  lashing  rope,  alcohol,  2  alcohol  lamps,  1  cable 
cutter,  cable  tags,  turk's  head,  collars,  cotton  waste,  4 
files,  4  hammers,  6  heaving  lines,  knives,  marline,  2  mar- 
line spikes,  1  megaphone,  2  monkey  wrenches,  4  j)liers, 
protective  tape,  rope,  rubber  cement,  rubber  tape,  2 
scissors,  1  set  of  stencil  numbers,  tin  foil,  and  a  measur- 
ing: line  which  has  marks  every  100  feet,  with  double 
marks  at  300  and  600  feet. 


13 

CORDAGE. 

1.  Name  the  important  knots  used  in  mine  work. 
Square  knot,   fisherman's  bend,   single  becket  bend, 

double  becket  bend,  stopper,  clove  hitch,  blackwall 
hitch,  cats'-paw,  rolling  hitch,  mooring  knot,  slip  knot, 
timber  hitch,  bowline,  sheepshank,  running  bowline, 
bowline  on  a  bight,  figure  of  eight,  short  splice,  throat 
seizing,  round  seizing. 

2.  The  mooring  rope  of  a  heavy  weight  can  not  pass  over 

the  winch,  but  lifting  must  be  done  with  the  fall;  ex- 
plain the  method  of  proceeding. 

This  condition  may  be  brought  about  when  there  are 
knots  in  the  raising  rope  that  will  not  pass  through 
the  snatch  block. 

Make  a  cats'-paw  in  the  raising  rope,  and  place  it 
over  the  hook  of  the  fall.  Eaise  the  fall  as  high  as  it 
will  go.  Put  a  stopper  around  the  raising  rope.  Slack 
away  on  the  fall.  Make  another  cat's-paw  above  the 
stopper  and  place  it  over  hook  of  fall.  Continue  as 
above  until  weight  of  anchor  is  high  enough  to  swing 
in-board. 

CARE    AND    PRESERVATION    OF    MINE    MATERIAL. 

1.  Name  the  supplies  necessary  for  cleaning  mine  material. 
Cotton  waste,  kerosene,  sandpaper,  emery  cloth,  alco- 
hol, scrapers,  wire  brushes. 

2.  Name  those  used  in  preserving  it,  stating  for  what  each 

is  used  and  how  they  are  applied. 

Cosmic,  white  lead,  red  lead,  raw  linseed  oil,  turpen- 
tine, drier,  lampblack,  beef  tallow  (rendered),  pumice 
stone,  varnish,  asphaltum  varnish,  paint  brushes. 


14 

When  oil  engines  or  motor  generators  are  out  of  com- 
mission their  bright  parts  should  ,be  covered  with  cos- 
mic. Brass  screw  threads  and  parts  of  tools  that  are 
liable  to  rust  should  also  be  so  smeared.  In  all  cases 
where  cosmic  is  used  on  bright  surfaces  to  prevent  cor- 
rosion it  should  be  applied  four  times  a  year. 

Screw  threads  of  mine  cases,  steel  screw  threads  of 
compound  plugs,  bolts,  nuts,  and  washers,  and  surfaces 
of  flat  joints  should  be  kept  smeared  with  a  slushing 
grease  made  of  1  part  white  lead  and  4  parts  beef  tal- 
low (rendered).  No  oils  or  grease  should  ever  be  placed 
on  points  where  metallic  contact  of  electrical  instru- 
ments are  necessary,  nor  on  india  rubber,  ebonite,  or 
slate. 

Mine  cases  should  rest  on  racks  or  skids,  and  where 
space  permits  should  not  be  in  contact  with  each  other. 
In  handling  mine  cases  care  must  be  taken  not  to  dam- 
age the  bails  or  bolts.  They  should  be  so  arranged 
that  the  holes  in  the  mine  cases  can  be  easily  seen; 
these  holes  should  be  fitted  Avith  a  wooden  plug  which 
has  been  thoroughly  greased  all  over  its  surface.  New 
mine  cases,  if  galvanized,  usually  will  not  need  paint- 
ing until  they  have  been  in  the  water.  AVhen  taken 
from  the  water  they  should  be  thoroughly  dried,  and  if 
they  should  show  signs  of  rust,  they  should  be  gone 
over  thoroughly  with  steel-wire  brushes  until  the  rust 
is  removed.  Parts  which  can  not  be  reached  with  the 
brush  should  be  cleaned  with  three-cornered  steel  scrap- 
ers. A  heavy  coat  of  red  lead  should  then  be  applied ; 
7  gallons  of  this  paint  can  be  made  by  mixing  100 


15 

pounds  of  red  lead  ground  in  oil  with  5  gallons  of  raw 
linseed  oil.  This  mixture  should  be  applied  within  two 
or  three  weeks  after  mixing.  One  gallon  of  paint 
should  give  ten  mine  cases  one  coat.  After  this  coat 
has  been  allowed  to  dry  there  should  be  applied  a  coat 
of  white  lead  toned  down  to  a  /neutral  gray.  Seven  gal- 
lons of  this  paint  can  be  made  by  mixing  100  pounds 
Avhite  lead,  2^  gallons  raw  linseed  oil,  2^  gallons  tur- 
pentine, 1  gallon  liquid  drier,  and  adding  about  1  pound 
of  lampblack  to  tone  down  the  mixture. 

Should  loose  paint  or  rust  be  seen  the  case  should  be 
repainted.  A  small  wooden  mallet  may  be  used  to  tap 
the  case  at  all  points  to  loosen  scales  of  rust  or  paint; 
then  the  surface  should  be  thoroughly  wire  brushed  or 
scraped  and  the  cases  repainted  as  stated  above. 

If  the  oil  engine  has  not  been  painted,  it  should  be 
given  a  priming  coat  of  red  lead  mixed  in  oil.  This 
should  be  rubbed  down  with  pumice  stone  and  two 
coats  of  steel-colored  paint  applied.  The  second  coat 
should  be  rubbed  down  and  two  coats  of  varnish  then 
applied.  After  this  the  engine  should  not  need  re- 
painting for  a  couple  of  years.  When,  however,  re- 
painting is  necessary,  the  engine  should  be  rubbed  down 
until  all  varnish  is  removed  and  a  coat  of  steel-colored 
paint  applied.  This  coat  should  be  rubbed  until  no 
brush  marks  remain,  and  one  or  two  coats  of  varnish 
should  then  be  applied.  The  steel-colored  paint  should 
be  applied  flat — that  is,  the  color  which  is  ground  in 
japan  should  be  mixed  with  turpentine.  One  gallon  of 
this  paint  is  more  than  sufficient  to  give  an  engine  two 
coats. 


16 

The  motor  generators  and  casemate  transformer  usu- 
ally will  not  need  the  priming  coats  of  red  lead,  as  they 
generally  come  from  the  factory  painted.  AVhen  it  is 
necessary  to  paint  them,  one  coat  of  the  steel-colored 
paint  and  one  of  varnish  Avill  usually  be'  found  suffi- 
cient. 

Anchors,  distribution  boxes,  mooring  sockets,  shac- 
kles, sister  hooks,  junction  boxes,  and  the  iron  work  of 
operating  boards  and  power  panels  should  be  painted 
with  asphaltum  varnish. 

Paint  brushes,  when  new,  and  before  using,  should 
be  wrapped  or  bridled  with  strong  twine  and  soaked  in 
water  to  swell  up.  After  using,  they  should  be  cleaned 
with  turpentine  and  put  away  in  Avater  to  keep  them 
from  drying  and  becoming  unpliable. 

Large  ropes  should  be  stored  on  skids,  allowing  a 
free  circulation  of  air.  Small  ropes  should  be  hung  on 
wooden  pins.  Eopes  should  be  uncoiled  semiannually 
in  dry  seasons  and  stretched  out  for  several  days  to 
dry. 

HIGH   EXPLOSIVES. 

1.  What  high  explosives  are  used  in  mines? 
Dynamite,  wet  gun  cotton,  and  in  emergency  other 

commercial  high  explosives. 

2.  What   are  the   important   precautions   to   be   observed   in 

loading  mines? 

In  handling  boxes  of  high  explosive,  the  greatest  care 
must  be  observed.  Eubbers  must  be  worn  by  those  en- 
tering the  magazine.     The  boxes  must  not  be  dropped 


17 

or  slid  either  upon  one  another  or  upon  the  floor  or 
skids,  but  must  in  every  case  be  lifted  bodily.  They 
must  not  be  left  exposed  to  the  direct  rays  of  the  sun 
nor  stored  in  a  building  in  which  the  temperature  rises 
unduly. 

In  loading  mines  only  one  box  of  explosive  for  each 
loading  party  is  brought  to  the  loading  room  at  a  time. 
As  soon  as  dynamite  is  removed  from  the  boxes,  they, 
with  their  sawdust  packing,  must  be  carefully  removed 
to  a  safe  place  and  subsequently  burned.  A  piece  of 
bagging  or  canvas  is  spread  upon  the  floor  in  the  load- 
ing room,  and  the  mine  case  is  placed  on  this  on  skids. 
The  loading  funnel  is  placed  in  the  opening  in  the  case, 
and  the  cakes  or  cartridges  are  passed  in  by  hand  until 
the  entire  charge  has  been  inserted.  In  loading  dyna- 
mite the  cartridges  should  be  handled  with  rubber 
gloves  and  should  be  brushed  off  over  the  box  as  they 
are  removed.  Constant  care  is  taken  that  no  small 
particles  of  this  explosive  are  dropped  where  they 
might  be  trodden  under  foot  or  subjected  to  friction 
in  moving  the  mine  case.  The  floor  is  frequently 
swept,  the  dust,  litter,  pieces  of  paper,  etc.,  being- 
removed  to  a  distance  and  burned.  The  cartridges  are 
so  placed  that  they  will  not  be  torn  up  by  the  com- 
pound plug  when  the  latter  is  screwed  home.  AVhen  the 
charge  has  been  inserted,  the  funnel  is  removed  aiid 
the  threads  very  carefully  cleaned  with  a  soft  brush. 
Before  inserting  the  compound  plug  the  threads  are 
completely  smeared  with  ruberine  or  som.e  similar 
substance. 

22092—08 2 


18 

For  a  charge  of  djmamite  the  primer  charge  is  1 
pound  of  loose  dynamite  contained  in  a  small  bag, 
which  fits  easily  into  the  fuze  can.  In  filling  the  bag, 
rubber  gloves  must  be  worn.  To  insert  the  fuzes,  the 
bag  is  opened  and  the  fuzes  are  embedded  in  the  ex- 
plosive, the  choke  of  the  bag  being  then  tied  around  the 
fuze  wires. 

For  a  charge  of  wet  gun  cotton,  the  primer  charge  is 
of  dry  gun  cotton.  This  may  be  either  of  crumbled  gun 
cotton  or  of  cakes  cut  to  fit.  The  compressed  primers 
are  supplied  wet  and  consist  of  three  cakes,  one  of  which 
is  bored  with  two  i%-inch  holes  to  receive  the  fuzes. 

It  is  essential  that  the  gun  cotton  primer  be  thor- 
oughly dry.  It  is  not  safe  to  saw  or  bore  a  dry  gun 
cotton  cake. 

The  mine  fuze  is  the  regular  commercial  electric  fuze, 
double  strength,  extra  quality,  and  containing  24  grains 
mercuric  fulminate.  The  lead  wires  need  not  be  over 
7  inches  in  length. 

Mines  charged  with  wet  gun  cotton  may  be  safely 
unloaded,  using  ordinary  precautions.  The  compound 
plug  being  unscrewed,  the  cakes  are  removed  by  hand, 
repacked  in  the  original  boxes,  a  little  fresh  water 
added,  and  the  boxes  closed. 

In  unloading  mines  charged  wdth  dynamite  too  many 
precautions  can  not  be  taken.  The  mine  should  be  held 
either  in  an  opening  in  a  raft,  or  behind  an  earthen 
traverse,  and  the  compound  plug  removed  by  some 
arrangement  which  may  be  operated  from  a  safe  dis- 
tance. If  the  mine  has  been  planted  for  some  time,  the 
recovered  dynamite  is  usually  destroyed. 


19 

Sometimes  the  mine  cases  will  be  found  to  be  coated 
with  an  extremely  sensitive  film  of  exuded  nitroglyc- 
erin. This  film  may  be  destroyed  by  filling  and  thor- 
oughly rinsing  the  case  with  "  sulfur  solution  "  pre- 
pared by  boiling  20  pounds  of  powdered  sulfur  and  50 
pounds  of  lime  in  a  barrel  of  water. 

3.  How  is  frozen  dynamite  thawed? 

The  thawing  of  it  near  a  stove  is  strictly  prohibited. 

The  best  method  is  to  leave  the  boxes  open  for  several 
hours  in  a  warm  room.  If  time  be  lacking,  the  dyna- 
mite may  be  thawed  by  placing  it  in  an  open,  water- 
tight can  and  placing  the  can  in  warm  water  not  hotter 
than  can  be  easily  borne  by  the  hand. 

4.  Where   is  the  main  supply  of  explosive  kept,   and  how 

much  is  taken  out  at  one  time  to  the  explosive  house 
near  the  loading  room? 
It  should  be  kept  in  cool  magazines,  in  which  the  tem- 
peratures does  not  fall  below  45°  F.,  and  where  there  is 
no  dripping  of  water.     Only  so  much  is  taken  to  the 
explosive  house  as  is  needed  for  immediate  use. 
♦ 

THE  PLOTTING  BOARD. 
1.   Describe  the  plotting  board. 

The  plotting  board  is  a  smooth,  usually  semicircular 
board  of  such  size  that  with  a  suitable  scale,  100  or  150 
yards  to  the  inch,  the  positions  of  all  the  mines  and  of 
the  primary  and  secondary  stations  may  be  located  with 
respect  to  each  other  on  a  sheet  of  paper  fastened  to  it. 

The  radius  of  the  board  supplied  by  the  Ordnance 
Department  is  40  inches. 


20 

Mounted  on  the  board  and  pivoted  one  at  the  location 
of  primary  station  and  the  other  at  secondary  station 
are  two  graduated  metal  arms.  The  scale  on  the  arms 
should  ordinarily  be  100  or  150  yards  to  the  inch. 
Each  arm  has  a  corresponding  azimuth  circle  with  de- 
grees numbered  with  respect  to  a  fixed  line. 

By  using  an  auxiliary  arm  supplied  on  boards  issued 
by  the  Ordnance  Department  only  one  circle  with  sep- 
arate graduations  for  each  station  is  necessary. 

By  means  of  index  boxes  at  the  outer  ends  of  the 
arms  they  may  be  set  to  hundredths  of  a  degree  and 
locked  in  position  for  all  necessary  azimuths  from  the 
station  to  which  each  arm  corresponds.  The  intersec- 
tion of  these  arms  which  have  been  set  to  simultaneous 
azimuths  from  the  two  stations  gives  the  location  of 
the  target  for  the  instant  the  observations  were  taken. 

2.   Explain  the   method   of    computing   the   time    from   any- 
plotted  point  to  a  mine. 

Positions  are  plotted  at  some  fixed  interval,  say  every 
20  seconds.  Knowing  the  distance  traveled  in  20  sec- 
onds, which  is  readily  determined  by  measuring  with  a 
speed  rule,  we  can*  determine  the  speed  of  the  target. 
Knowing  the  speed  of  the  target  and  how  far  it  must 
travel  until  it  will  come  within  the  destructive  radius 
of  a  mine,  we  can  determine  how  many  seconds  will 
elapse  from  the  time  of  the  last  plotted  position  until 
the  command  "  fire  "  is  given.  It  will  be  seen  that  the 
time  for  a  target  to  travel  from  any  plotted  point  to  a 
mine  will  depend  on  tAvo  things — the  speed  of  the  tar- 
get and  its  distance  from  the  mine.     Graphical  tables 


21 

have  been  constructed  with  all  values  of  the  speed  and 
distance  likely  to  occur  in  practice.  A  speed  rule  is 
furnished  for  measuring  distances  on  the  plotting 
board.  It  is  only  necessary  to  refer  to  the  table  to  take 
out  the  desired  time. 

3.   Act  as  plotter. 

This  should  be  done  at  the  plotting  board.  Briefly 
the  method  is  as  follows: 

An  assistant  No.  1  sets  the  arm  at  the  angle  as  given 
from  the  primary  station.  No.  2  sets  his  arm  at  the 
angle  as  observed  at  the  secondary  station  at  the  same 
instant.  The  intersection  gives  the  position  of  the 
target  at  the  instant  and  is  plotted  by  the  plotter.  Suc- 
cessive positions  thus  determined  will  give  the  course 
and  the  speed  of  the  target.  It  is  thus  possible  to  de- 
termine if  the  target  will  cross  the  plotted  position  of 
a  mine  and  how  many  seconds  will  elapse  before  that 
event  will  occur.  Accuracy  and  speed  are  both  neces- 
sary, but  the  former  must  not  be  sacrificed  for  the 
latter.     Speed  will  come  with  practice. 

BATTERIES,    GENERATORS,    AND    SEARCHLIGHTS 
ASSIGNED   TO   THE   COMPANY. 

1.  Name  the  batteries  used  in  mine  work. 

Casemate  battery,  consisting  of  40  storage  cells,  and 
boat  telephone  battery,  consisting  of  sufficient  dry  cells 
to  give  approximately  15  volts. 

2.  Describe  the  casemate  battery. 

This  is  a  40-cell  chloride  accumulator  with  a  normal 
charge  and  discharge  rate  of  5  amperes.    The  voltage 


22 

may  be  taken  at  2  volts  per  cell.  The  type  of  cell  is 
D-5,  in  which  the  letter  denotes  the  size  of  plate,  and 
the  figure  the  number  of  plates  per  cell.  In  the  type 
used  for  the  submarine  mine  work,  there  are  two  posi- 
tive plates  and  three  negative  plates  in  each  cell.  The 
positive  plates  are  of  a  brownish  color,  sometimes  called 
plum  colored.  The  negative  plates  have  a  grayish 
color.  When  the  battery  is  set  up,  the  cells  rest  on 
sand  trays  and  the  trays  on  glass  insulators.  This  is 
to  thoroughly  insulate  the  battery.  The  jars  are  partly 
filled  wdth  electrolyte,  which  is  a  mixture  of  sulphuric 
acid  and  Avater,  having  a  specific  gravity  of  1.210. 

3.   What  precautions  are  necessary  to  keep  it  in  order? 

When  the  battery  is  in  regular  service,  the  discharge 
should  not  be  continued  below  1.8  volts  per  cell  at  full 
load.  The  charging  should  be  started  at  once  after  a 
discharge  and  continued  until  the  battery  is  fully 
charged.  The  cells  must  never  be  allowed  to  stand  dis- 
charged. If  by  chance  this  should  happen,  the  charg- 
ing must  be  proceeded  with  at  half  rate. 

The  battery  should  be  discharged  and  charged  at 
least  once  a  Aveek  and  record  must  be  kept  of  each  cell, 
show^ing  its  voltage  and  specific  gravity.  It  is  custom- 
ary to  read  the  voltage  just  before  the  end  of  the 
charge  and  the  specific  gravity  immediately  after  shut- 
ting off  the  charging  current.  Cells  must  be  inspected 
for  short  circuit  and,  if  any  exist,  a  piece  of  hard  rub- 
ber or  glass  used  to  remove  them.  Metal  must  not  be 
used  under  any  circumstances.  Water  should  be  added 
to  the  cells  at  the  beginning  of  the  charge  to  bring  the 


23 

electrol}^te  to  the  proper  height.  ^^Tien  the  specific 
gravity  of  the  electrolyte  at  the  end  of  an  overcharge 
and  at  normal  temperature  has  fallen  to  1.190,  it  should 
be  brought  up  to  standard  by  the  addition  of  1.400  acid 
instead  of  water,  when  replacing  evaporation,  provided 
the  cell  is  in  good  condition  otherwise.  The  indications 
of  a  full  charge  are  the  appearance  of  the  plates — the 
deep  chocolate  color  of  the  positive  plates  and  the  light 
slate  color  of  the  negative  plates;  the  gassing  of  the 
cells;  the  readings  of  the  voltmeter,  about  2.50  per  cell; 
the  specific  gravity  of  each  cell  near  1.210. 

4.   Describe  a  searchlight. 

The  essential  parts  of  a  searchlight  are  a  reflecting 
surface  placed  behind  a  light  together  with  some  means 
of  directing  the  reflected  rays  in  any  desired  direction. 
All  the  searchlights  in  the  United  States  service  are 
fitted  with  parabolic  ground  glass,  silver  plated  mir- 
rors or  parabolic  metallic  gold-plated  mirrors  for  re- 
flection surfaces.  The  reflectors  are  furnished  in  the 
following  sizes:  18-inch,  24-inch,  30-inch,  36-inch,  and 
60-inch.  For  artillery  purposes  probably  the  36-inch 
and  60-inch  lights  will  be  employed.  These  two  may 
be  controlled  by  hand  or  by  an  electric  controller  at  the 
w411  of  the  operator.  There  are  means  provided  for  ad- 
justing the  carbons  so  as  to  bring  the  electric  arc  into 
proper  focus.  The  carbons  are  fed  toward  each  other 
automatically,  means  being  provided  for  feeding  the 
positive  carbon  twice  as  fast  as  the  negative  to  allow  for 
its  more  rapid  consumption.  Other  parts  of  the 
searchlight  are  motors  for  traversing  and  for  elevating 


24 

and  depressing;  controller  switch;  focusing  screw; 
socket  for  inserting  wrench  to  operate  lamp  switch  used 
for  cutting  out  feeding  magnet;  socket  for  inserting 
w^rench  when  feeding  by  hand;  wheel  for  slow  vertical 
movement;  wheel  for  slow  horizontal  movement;  base; 
carbon  holders;  lamp;  doors  for  adjusting  the  carbons 
and  for  cleaning  the  front  door. 

5.   Describe  parts  of  generators  and  important  points  to  be 
observed  in  caring  for  them. 

The  principal  parts  of  the  generator  are :  The  arma- 
ture, brushes  and  holders,  commutator,  field  coils  and 
magnets,  frame,  and  base  plate.  The  generator  should 
be  kept  clean  and  dry.  If  the  casemate  is  damp  it  may 
be  necessary  to  take  special  precautions  against  damp- 
ness, wiping  off  the  moisture  so  far  as  possible  and  dry- 
ing out  the  casemate  w^th  an  oil  stove,  if  other  means 
of  heating  have  not  been  provided.  Wlien  moisture  is 
present,  it  is  Avell  to  run  the  generator,  as  this  will  help 
to  dry  the  machine. 

The  belt  between  the  engine  and  dynamo  should  not 
be  too  tight.  The  dynamo  should  be  fastened  to  a  firm 
foundation  Avith  anchor  bolts  and  should  be  well  insu- 
lated by  using  a  layer  of  dry  wood  between  the  con- 
crete and  the  base  plates.  The  best  dynamo  oil  should 
be  used  for  the  bearings.  Commutators  should  be  clean 
and  smooth,  and  the  brushes  should  fit  on  them  with 
large  contact  surfaces.  The  commutator  should  be 
cleaned  occasionally  with  a  little  oil  or  vaseline,  being 
carefully  wdped  as  dry  as  possible  after  cleaning.  The 
machine  should    run    smoothly  without    any    unusual 


25 

noises  and  without  undue  heating  of  its  bearings  on 
account  of  friction.  The  armature  of  the  casemate 
machine  is  not  well  ventilated,  and  it  heats  unduly.  The 
machine  must  be  carefully  watched  and  on  the  first  sign 
of  undue  heating  the  dynamo  should  be  stopped  and 
allowed  to  cool.  Water  should  never  be  poured  on  it 
to  cool  it.  The  brushes  should  be  so  adjusted  that,  when 
running  at  full  speed,  no  sparking  occurs  at  either  end. 
The  best  position  of  the  brushes  is  found  by  trial, 
and  the  position  should  then  be  marked  so  that  if  dis- 
turbed they  can  be  put  back  in  place  readily.  The 
machine  should  be  covered  when  not  in  use.  AH  elec- 
trical connections  should  be  clean  and  firmly  made. 
Any  unnecessary  resistance  in  circuits  between  casemate 
battery  and  switchboard  and  between  dynamo  and 
switchboard  is  harmful  and  should  be  guarded  against. 

CASEMATE  APPARATUS  AND  ITS  CARE  AND 
OPERATION. 

1.   Name  the  apparatus  on  the  power  and  operating  panel. 

The  power  panel  has  mounted  on  it :  A  milli-ammeter 
and  protecting  lamp,  a  double-pole  circuit  breaker,  a 
single-pole  reverse  current  circuit  breaker,  a  two-way 
direct  current  ammeter,  a  direct-current  voltmeter,  an 
alternating  current  voltmeter,  double-pole  double-throw 
lever  switches,  double-pole  single-throw  lever  switches, 
receptacles,  plugs,  switchboard  lamps,  direct  current 
bus  bars,  alternating  current  bus  bars,  charging  rheo- 
stat, field  rheostat,  special  resistance  for  reverse  current 
circuit  breaker,  terminal  strips,  fuzes,  fuze  clips  and 
necessary  connections. 


26 

The  operating  panel  has  mounted  on  it  1  signal 
block,  1  master  block,  19  mine  blocks,  a  cable  terminal 
block,  brass  bus  bars  and  necessary  connections. 

The  signal  block  has  mounted  on  it  a  single-stroke 
signal  gong,  a  single-pole  gong  switch,  16-candlepower 
45-volt  red  lamp  and  base,  16-candlepower  110-volt 
white  lamp  and  base,  16-candlepower  45-volt  green 
lamp  and  base,  resistance  coil  in  parallel  with  white 
lamp  with  clips,  earth  (or  bell)  terminal,  alternating 
current  terminal,  and  direct  current  terminal. 

The  master  block  has  mounted  on  it  an  A.  C.  jaw,  a 
D.  C.  jaw,  testing  switch,  and  a  firing  switch.  A 
jumper  with  terminals  is  provided  for  use  with  A.  0. 
and  D.  C.  jaw^s. 

Each  of  the  19  mine  blocks  has  mounted  on  it:  One 
single  pole  double  throw  testing  switch,  1  single  pole 
double  throw  automatic  switch  with  through  pin  for 
closing  red  lamp  and  bell  circuit,  1  mine  switch,  and  1 
D.  C.  power  switch;  necessary  connections  to  bus  bars 
and  terminal  block,  and  2  screws  for  mounting  block  on 
frame  are  also  provided.  Mine  blocks  even  if  of  dif- 
ferent makes  are  interchangeable  among  different  pan- 
els or  on  same  panel.  The  terminal  block  is  provided 
with  19  numbered  binding  posts  and  clips. 

2.   Describe    the    motor    generator,     casemate    transformer, 
mine  transformer,  and  boat  telephone. 

The  motor  of  the  motor  generator  is  a  1^-horsepower 
bipolar  D.  C.  shunt  machine  designed  to  operate  on  a 
voltage  of  from  80-110.  This  motor  is  direct  con- 
nected to  a  4  pole  single-phase  A.  C.  generator,  giving  a 


27 

voltage  approximately  equal  to  that  impressed  on  the 
motor. 

The  casemate  transformer  is  a  one-half  kilowatt  step- 
up  transformer,  ratio  79 :  500 ;  the  oil  used  to  cool  the 
coils  is  ordinary  transformer  oil  and  the  case  should  be 
kept  filled  with  this  oil. 

The  mine  transformer  is  a  step-down  transformer 
with  a  high  resistance  primary.  The  circuit  is  com- 
pleted through  this  primary  by  grounding  one  end  to 
the  case.  Further  details  of  the  mine  transformer  will 
be  supplied  by  the  instructor  if  necessary. 

The  boat  telephone  is  a  hand  telephone  consisting  of 
transmitter,  receiver,  condenser,  buzzer,  talking  key, 
calling  key,  and  a  small  nickel-plated  metal  case  contain- 
ing all  the  above-mentioned  parts.  There  is  a  choke 
coil  between  each  side  of  the  15-volt  battery  and  the 
line.  Both  coils  are  inclosed  in  one  case.  This  set  of 
coils  is  not  necessary  unless  there  are  two  or  more  lines 
being  operated  simultaneously  from  the  same  battery. 

3.   Explain  how  to  set  the  power  panel  and  operating  panel 
for  automatic  firing. 

(a)  See  that  all  lamps  on  signal  block  are  screwed 
home  and  bell  switch  closed. 

(b)  See  that  all  four  switches  on  each  mine  block 
are  closed  up  (i.  e.,  testing  switch,  automatic  switch, 
mine  switch,  and  poAver  switch),  except  on  blocks  be- 
longing to  mines  which  have  been  fired.  On  these 
blocks  the  power  and  mine  switches  should  be  open. 

(«?)  At  the  power  panel.  Put  power  on  D.  C.  busses 
in  one  of  the  following  ways: 


28 

1.  Close  both  poles  of  double  pole  circuit  breaker,  or 

2.  Close  single  pole  reverse  current  circuit  breaker 
and  switch  No.  2  to  the  right,  or 

3.  With  engine  and  casemate  generator  running,  close 
single  pole  reverse  current  circuit  breaker  and  switch 
No.  2  to  the  left. 

In  each  of  the  three  cases  (1),  (2),  and  (3)  put  plug 
in  proper  receptacle  to  give  on  D.  C.  voltmeter  the  volt- 
age of  circuit  to  be  used.  Read  voltmeter  to  see  if 
proper  voltage  is  on  the  busses.     For  storage  battery 

(1)  this  should  be  from  80  to  85  volts.    For  post  power 

(2)  this  would  be  probably  from  110  to  125  volts.  For 
casemate  generator  (3)  this  should  be  80  to  110  volts; 
regulate  this  to  value  desired  by  means  of  field  rheostat. 

{d)   Close  switch  No.  3  up. 

{e)  Close  switch  No.  4  up  (or  down). 

(/)   Close  switch  No.  9  up  (or  down). 

Ig)  Put  A.  C.  plug  in  proper  receptacle  and  read  A. 
C.  bus  bar  voltage. 

This  should  be  at  least  500  volts.  If  storage  battery 
is  on  busses  and  the  A.  C.  bus  bar  voltage  does  not  read 
at  least  500,  raise  to  500  by  cutting  out  resistance  of 
charging  rheostat. 

(A)   Close  switch  No.  8  up. 

{i)  Examine  all  automatic  switches  again  and  if  any 
of  them  are  down  close  them  up,  and  if  any  one  will 
not  remain  closed  by  adjusting  the  solenoid  plunger 
open  the  power  switch  on  this  particular  mine  block. 

{k)   Close  firing  switch. 


29 

4.  Explain  how  to  test  mines  when  planted. 
With  D.  C.  on  D.  C.  bus  bars. 

(a)  Unscrew  the  green  lamp  on  all  signal  blocks  ex- 
cept the  one  on  the  panel  to  which  the  mine  being 
tested  belongs. 

(h)  Open  the  power  switch  on  each  mine  block  on 
the  panel  to  which  the  mine  being  tested  belongs.  All 
other  switches  on  these  mine  blocks  should  be  closed  up. 

(c)  Close  switch  No.  3  down. 

(d)  Close  the  power  switch  of  the  mine  being  tested 
up  and  note  corresponding  reading  on  the  milliam- 
meter. 

This  reading  should  under  normal  conditions  be  from 
30  to  40  milliamperes,  but  the  mine  is  still  in  a  serv- 
iceable condition  if  the  reading  be  as  low  as  14  or  as 
high  as  170  milliamperes. 

5.  How  are  boat  telephones  operated? 

One  terminal  of  the  casemate  boat  telephone  is  con- 
nected to  either  side  of  the  telephone  battery,  and  the 
same  terminal  of  the  battery  is  connected  to  the  multi- 
ple cable  core  in  use  (1,  13,  or  19),  usually  through  the 
corresponding  mine  switch  jaw.  This  switch  should 
be  open.  The  other  terminal  of  the  phone  is  connected 
to  earth.  This  may  be  conveniently  done  through  the 
lower  jaw  of  the  testing  switch.  The  other  terminal 
of  the  battery  has  a  permanent  connection  to  earth. 

The  boat  telephone  in  use  on  the  water  has  either  ter- 
minal connected  to  the  same  cable  core  to  which  the 
casemate  boat  telephone  is  connected. 


30 

The  other  terminal  of  this  phone  is  earthed  either  by 
connecting  it  to  the  armor  of  the  cable  or  by  connecting 
it  to  an  earth  plate  and  dropping  the  plate  overboard. 
To  call,  press  the  button.  To  talk,  hold  down  the  talk- 
ing key. 

o 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 

AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED   FOR   FAILURE  TO   RETURN 
THIS    BOOK   ON   THE   DATE   DUE.    THE  PENALTY  . 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY    AND     TO     $1.00     ON     THE    SEVENTH     DAY 
OVERDUE. 

DEC  lil939 

YB  49809 


^ 


^^■^■^J^ 


165930 


